Commercial vehicles are commonly equipped with a compressed air storage system for operating air brakes and other pneumatically activated devices. An air compressor driven by the vehicle engine supplies compressed air to one or more storage vessels, which in turn are coupled to the air brakes and other pneumatically activated devices. Since excessive ambient moisture in the compressed air can be harmful to air brakes and other pneumatically activated devices, most compressed air storage systems include a moisture removal mechanism.
One of the most common and cost effective ways to remove moisture from a compressed air storage system is to drive the compressed air through a desiccant material such as silica gel or active alumina that adsorbs moisture on its surface. At some point, the desiccant material becomes saturated and the adsorbed water must be removed through a regeneration procedure. However, the problem with this approach is that air supplied by an oil-lubricated compressor invariably contains a certain amount of blow-by oil mist that contaminates the desiccant material so that it will no longer adsorb moisture or regenerate. This condition can be forestalled to some degree by installing an oil filter upstream of the desiccant, but both the oil filter and the desiccant material must, as a practical matter, be periodically replaced to keep the brakes and other pneumatically activated devices free of excessive moisture. Accordingly, what is needed is a more reliable and maintenance-free apparatus for removing excessive moisture in a motor vehicle compressed air storage system.